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Peer to peer

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Transcript

  • 1. Peer-to-Peer System Raviteja Adusumalli ali@sics.se 1
  • 2. Definition• What is a distributed system? ”You know you have a distributed system when the crash of a computer you have never heard of stops you from getting any work done.” Leslie Lamport We counteract this definition! ali@sics.se 2
  • 3. Distributed Systems• Example of distributed systems: – File systems Frequently, an organization – Web servers stores all its files on a centralized distributed file server – Mail servers If it fails, no one can access their – Databases files The central mail server crashes, no one can read their Webb servers often become email! overloaded and fail ali@sics.se 3
  • 4. Our effort• Build on an 30-year old idea• Arpanet, the precursor of Internet, was built for: – Military survivability • If some part stops working, the rest should continue to function• Internet has been quite successful so far… – No fail-stop yet• But the effort stopped here… ali@sics.se 4
  • 5. Peer-to-Peer System• We want to build – Services – Servers – Applications• That are self-managed• Achieved by peer-to-peer techniques! ali@sics.se 5
  • 6. Peer-to-Peer Middleware• After several years of research – Built a middleware: DKS• Provides: – Routing services – Directory services – Name-based messaging (multicast/publish/subscribe) ali@sics.se 6
  • 7. Peer-to-Peer System• DKS is self-managing• Automatic managent: – Adding servers/resources – Removing servers/resources – Crash of servers/resources – Load balancing of data/nodes – Security ali@sics.se 7
  • 8. Peer-to-Peer?• How is it different from: – KaZaa – Napster – Gnutella – Skype• These are so called unstructured p2p systems – Limited applicability (file sharing) – Inefficient (wastes bandwidth)• Our focus is on structured p2p systems – Chord/CAN/Pastry (USA) – DKS/P-Grid (Europe) ali@sics.se 8
  • 9. What can we do with DKS?• Three concrete applications: – P2P Web server – P2P Backup – P2P File system ali@sics.se 9
  • 10. P2P Web• Works like an Publish your web pages ordinary web server• Differences: – It is distributed – Automatic data Gets stored on the DKSStore a copy here replication 15 0 Store it here 1 – Load-balancing 14 15 1 2 of users 13 13 3 4 12 4• Too much load 5 – Add another 11 5 server Store a new copy here 10 6 9 7 8 ali@sics.se 10
  • 11. P2P Backup• Initialization – Install a client on your computer – Decide on amount of space to share – Choose files for backup• Regular backup – Data is encrypted – Always accessible ali@sics.se 11
  • 12. Conclusion• Structured Peer-to-Peer system – Self-organizing • Automatic fault-tolerance • Automatic addition of nodes/resources • Automatic removal of nodes/resources • Automatic load-balancing• Many interesting applications – File systems – Backup – Web – M.m.• Cost-saving for companies – Save money on administration ali@sics.se 12